Emergency retraction means for the manipulator arm of a nuclear  reactor vessel inspection apparatus

ABSTRACT

An emergency retraction means is provided for removing the extended manipulator arm of a nuclear reactor vessel inspection device from within a nozzle thereof or from a fully extended position should power for normal extension drive fail. A cable is looped about the interior of a carriage assembly which drivingly engages the remainder of the manipulator arm. The cable is fixedly clamped at one location within the carriage assembly and looped about a first idler pulley mounted in the manipulator arm and is guided therefrom by another idler to an accessible point where the end of the cable is formed into a ring. The ring is detachably secured thereat to the carriage assembly. 
     When an emergency occurs, a hook is lowered to engage the ring and is then lifted to detach it from the carriage assembly and move it upwardly therefrom. As the ring is pulled up, it tightens the cable about the first idler pulley pulling it towards the main column of the inspection device and mechanically forcing the manipulator arm extension drive to manually retract the manipulator arm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is hereby cross-referenced to the following patentapplications which were commonly filed herewith and which are commonlyassigned:

U.S. Pat. application Ser. No. 781,403 filed Mar. 25, 1977, entitled"Positioning Means For Circumferentially Locating Inspection ApparatusIn A Nuclear Reactor Vessel", filed in the name of David C. Burns;

U.S. Pat. application Ser. No. 781,381, filed Mar. 25, 1977, entitled"Segmented Articulating Manipulator Arm For Nuclear Reactor VesselInspection Apparatus", filed in the names of David C. Burns and LansonY. Shum;

U.S. Pat. application Ser. No. 781,380, filed Mar. 25, 1977, entitled"Variable Mounting Assembly For Transducers Employed In Nuclear ReactorVessel Inspection Apparatus", filed in the names of Hans J. Elsner,Ronald F. Antol and Raymond P. Castner;

U.S. Pat. application Ser. No. 781,390, filed Mar. 25, 1977, entitled"Pulley System Including Emergency Locking Means For Nuclear ReactorVessel Inspection Apparatus", filed in the name of Renato D. Reyes;

U.S. Pat. application Ser. No. 781,396, filed Mar. 25, 1977, entitled"Emergency Braking System For Nuclear Reactor Vessel InspectionApparatus", filed in the name of Renato D. Reys;

U.S. Pat. application Ser. No. 781,396, filed Mar. 25, 1977, entitled"Emergency Disconnect Means For The Manipulator Arm Of A Nuclear ReactorVessel Inspection Apparatus", filed in the names of Arthur F. Jacobs andDuane W. Morris; and

U.S. Pat. application Ser. No. 781,404, filed Mar. 25, 1977, entitled"Pressurized Cabling And Junction Boxes For Nuclear Reactor VesselInspection Apparatus", filed in the names of Charles V. Fields andRaymond P. Castner.

BACKGROUND OF THE INVENTION

Nuclear reactor vessels employed in the commercial generation ofelectrical power are of two types; the pressurized water type or theboiling water type. In either case, the reactor vessel utilizes agenerally cylindrical metallic container having a base and a top flangewelded thereto. The main cylinder portion itself usually comprises aseries of lesser cylinders welded to each other. In addition, aplurality of circumferentially spaced nozzles extend through the maincylinder wall and are welded thereto. Thus, numerous welds arenecessarily used in fabricating the reactor vessel, in mating the topflange to the main cylindrical body and in securing the inlet and outletnozzles to the reactor vessel wall.

The reactor vessel, in use, is encased in a thick concrete containmentarea. However, the structural integrity of the reactor vessel, theconcrete containment nothwithstanding, due to the operating environmentis of critical importance.

The weld areas of the reactor vessel are, of course, inspected prior toits initial use. Such inspection is carried out with all portions of thevessel relatively accessible to an inspection device prior to itsencasement in the concrete containment. However, in-service inspectionof the reactor vessel welds is not only desirable, but is mandated undergovernmental regulations.

Under such regulations, it is required that the vessel weld areas besubjected to periodic volumetric examination whereby the structuralintegrity of the vessel is monitored. Due to the nature of an in-serviceinspection, the device designed to accomplish the specified weldexaminations must be capable of successfully operating in an underwaterand radioactive environment under remote control while maintaining ahigh degree of control over the placement and movement of the inspectionsensors.

The operating constraints are further complicated by the variety ofreactor vessel sizes to which the inspection device must be able to beaccommodated. Furthermore, the inspection device must not only becompatible with the weld placements of the reactor vessels now in use,but must also be sufficiently versatile to adapt to inspection duty infuture vessels. In addition, the inspection device must be arranged inits use to have only minimal impact with normal refueling andmaintenance operations.

The use of ultrasonic transducers to inspect metal welds is known. Onesuch system is described in the periodical Materials Evaluation, July1970, Volume 28, No. 7, at pages 162-167. This article describes atransmitter-receiver type ultrasonic inspection system for use in thein-service inspection of nuclear reactor vessels. The positioningarrangement for the transducers uses a track which is mounted on theinterior wall of the reactor vessel.

A method and apparatus for ultrasonic inspection of a pipe from withinis disclosed in U.S. Pat. No. 3,584,504. In the apparatus disclosedtherein, a transducer array is mounted on a carrier which is rotatable,by means of a central shaft of the apparatus, within the pipe.

In U.S. Pat. No. 3,809,607, a nuclear reactor vessel in-serviceinspection device is detailed, which device is adapted to permitremotely controlled and accurate positioning of a transducer arraywithin a reactor vessel. This device comprises a positioning and supportassembly consisting of a central body portion from which a plurality ofradially directed support arms extend. The ends of the support arms areextended to and adapted for being seated on a predetermined portion ofthe reactor vessel to define a positional frame and reference for theinspection device relative to the reactor vessel itself. Repositioningand support assemblies are provided and include integral adjustmentmeans which cooperate to permit the simultaneous variation of theextension of the support arms thereby allowing the inspection device tofit reactor vessels of differing diameters. A central column isconnected to the positioning and support assemblies, which centralcolumn extends along the longitudinal axis thereof. One or more movableinspection assemblies are connected to the central column and includedrive and position indicating means. Three specific inspectionsubassemblies include a flange scanner, a nozzle scanner and a vesselscanner. Each of these scanners employ multiprobe transmitter-receiverultrasonic transducers to permit more accurate volumetric plotting ofthe integrity of the welds used in fabricating the reactor vessel.

Since the development of the above-identified inspection devices, theoriginal inspection code has been amended to call for more reliable andmore rigorous inspections. In addition, these prior art devices wereunable to accurately measure or reach certain weld areas of the reactorvessel. Still other drawbacks in the prior art inspection devices werethe reliability and speed of the actual inspection effort.

One particular problem not solved by any of the above-described priorart devices is that of retracting the manipulator arm should anemergency occur while it is fully extended, particularly within one ofthe reactor vessel nozzles. Of specific concern is the situation wherepower fails with the manipulator arm so extended.

SUMMARY OF THE INVENTION

Accordingly, there is provided apparatus for manually retracting themanipulator arm of an inspection device from an extended positionthereof when the drive means for extending and retracting the arm isinoperable due to power failure. A cable is fixedly secured to themanipulator arm frame at a point proximate the central column of theinspection device. The cable is looped about an idler pulley orengageable member, which is cooperably coupled to the manipulator armdrive means, and attached to the manipulator arm at a point remote fromthe central column.

The other end of the cable is fastened to the manipulator arm frame at apoint proximate the central column by detachable clamping means. Thatend of the cable is formed into a ring, positioned to be accessible fromabove the vessel. When engaged by a hook lowered into the vessel, thering detaches from the frame and pulls the manipulator arm, by pullingon the idler pulley, back towards the central column. Guide surfaces areprovided within the manipulator arm frame to contact and guide the cableso that it exerts maximum force on the idler pulley as the cable ispulled upwardly by the ring.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of each of the drawing figures usedherein to describe the invention:

FIG. 1 shows an exploded view of a nuclear reactor vessel and theseveral welds made in the fabrication thereof;

FIG. 2 illustrates a representative view of an inspection site with theinspection apparatus seated in the reactor vessel;

FIG. 3 is an isometric view of the inspection apparatus;

FIG. 4 shows an isometric view of a bushing and clamp used to secureportions of the inspection apparatus shown in FIG. 3;

FIG. 5 shows a plan view, partly in section, of a mounting bracket usedto secure portions of the inspection apparatus shown in FIG. 3;

FIGS. 6, 7 and 8 are plan views, partly in section, of a liftingassembly employed to align, seat and remove the inspection apparatusshown in FIG 3;

FIGS. 9 and 10 are isometric views of the inspection apparatus showingthe manipulator arm thereof in two of its possible inspection positions;

FIG. 11 is a plan view of the reactor vessel's top and circumferentialflanges;

FIG. 12 is a plan view of a specially configured support shoe, utilizedto position the inspection apparatus within the reactor vessel, having akeyed plate bolted thereto;

FIG. 13 is a plan view, partly in section, of the shoe and bracket shownin FIG. 12;

FIG. 14 is a plan view of a locating key used in place of the bracketshown in FIGS. 12 and 13;

FIG. 15 is an isometric view of the manipulator arm used in theinspection apparatus shown in FIG. 3;

FIG. 16 is a schematic view of a pulley system which is incorporated inone of the drive assemblies for the manipulator arm;

FIG. 17 is a plan view, partly cut away, illustrating an emergencybraking system in its rest position;

FIG. 18 is a plan view of the emergency braking system shown in FIG. 17in its fully braked position;

FIG. 19 shows a partial cross-sectional view of the emergency brakingsystem depicted in FIG. 17;

FIG. 20 is an end view representation of a telescoping drive assemblyused, in part, to position the manipulator arm;

FIG. 21 is a plan view which representatively illustrates a manuallyoperated emergency restruction system;

FIG. 22 is an isometric representation of an emergency release systemfor partially disabling the linkage between segments of the manipulatorarm;

FIG. 23 is a schematic representation of a pressurized cabling assemblyutilized to connect and energize elements of the inspection apparatus;

FIGS. 24 and 25 are isometric views of a transducer array carried by themanipulator arm; and

FIGS. 26 through 33 are plan or isometric views, some in partialsection, illustrating the mounting assembly used for the transducersincluded in the array depicted in FIG. 24.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein identical reference numerals havebeen used in the several views to identify like elements, FIG. 1 showsan exploded view of a nuclear reactor vessel 10. While the vessel 10 maybe fabricated in differing ways, the overall cylinder which results fromwelding together the several smaller cylinders 12 is used herein as anillustrative example for purposes of this description. The severalwelds, A-K, shown in FIG. 1 are typically those which are to beinspected together with the stud holes 34 and the ligament areas 35therebetween of the vessel top flange 13. It will be understood by thosefamiliar with the inspection code requirements for nuclear reactorvessels, that not all of the welds A-K or the top flange 13 arenecessarily inspected at the end of one time period, but that anyinspection apparatus therefor must be capable of efficiently andaccurately determining the integrity of the vessel welds A-K and its topflange 13, at one time or in predetermined code specified groupings.Further, the inspection apparatus must be accurately positioned toaccomplish vessel interrogation without harming the top flange 13 and,in particular, its ability to form a proper seal with the vessel header(not shown).

FIG. 2 depicts an illustrative example of an inspection site. Theinspection apparatus 14 is shown therein seated in the reactor vessel10. Prior to inspection, the apparatus 14 is assembled using an erectionrig 5 partially shown. After assembly, the inspection apparatus 14 islowered by the site work crane 7 into the reactor vessel pool 11 andinto the vessel 10. The work bridge 9, also partially shown in FIG. 2,can be utilized as necessary.

The inspection apparatus 14 is illustrated in FIG. 3. It comprises aquick-disconnect lifting assembly 16, a support ring 18 having anannular key 19 attached thereto, three support legs 20A, 20B and 20C, ahead support assembly 22, a main column 24, a manipulator arm 26, atransducer array 28 and an overall control system 30 which includes anassortment of motors, resolvers and cabling, and is mainly resident in aconsole 31. These main elements cooperate, in a manner to be morespecifically described hereinafter, to permit inspection of the reactorvessel 10 in accordance with code requirements.

The inspection apparatus 14 is adapted to be lowered into the reactorvessel 10 and is shown in two of its many possible inspection positionsin FIGS. 9 and 10. Prior to insertion of the inspection apparatus 14,the reactor vessel header is removed and tapered guide studs 32, havingchamfered heads 33, are inserted into three of the stud holes 34 whichhave been designated for that purpose. With the guide studs 32 in place,the inspection apparatus 14 is fully lowered into the reactor vessel 10and positively seated therewithin, as shall be hereinafter explained.The guide studs 32 are engaged by guide stud bushings 36 which aremovably mounted to the support ring 18. Accurate circumferentialpositioning of the inspection apparatus 14 is accomplished through theemployment of the guide studs 32 and guide bushings 36 in conjunctionwith a specially adapted support leg show 88, to be more fully describedbelow.

The clearance between the guide stud bushings 36 and the guide studs 32is typically a maximum of only 3/8". Therefore, it is of criticalimportance that the inspection apparatus 14 be lowered into the reactorvessel 12 with the guide studs 32 and bushings 36 in near perfectalignment with each other. Alternatively stated, the inspectionapparatus 14, which is a relatively heavy piece of equipment, must beclosely aligned with respect to the vertical and horizontal axis or theguide bushings 36 will be cocked with respect to the guide studs 32causing the inspection apparatus 14 to hang up thereon, which mightresult in damage to the inspection apparatus 14, the guide studs 32 orthe reactor vessel 10. Thus, the lifting assembly 16 must be adjustableto accommodate the cantilevered weighting effect of manipulator arm 26and/or any weight distribution disparity in the inspection apparatus 14which would cause it to tilt from a level attitude as it is beinglowered. In addition, with the inspection apparatus 14 in place, thelifting assembly 16 must be quickly and readily removable to allow useof the inspection site work bridge 9 should that be necessary.

The lifting assembly 16 is shown in greater detail in FIGS. 6, 7 and 8.When secured to the inspection aparatus 14, it is engaged by the sitecrane 7 which connects to the "U" bolt assembly 42 coupled to itsuppermost portion. The "U" bolt assembly 42 is shown in FIG. 3. Acylindrical collar 44 having a stepped, star-shaped or cloverleaf bore46 is bolted to the top of the head support assembly 22. The crane 7 nowlowers the lifting assembly 16 until a spider 48 enters bore 46, asshown in FIG. 6. The lifting assembly is then manually rotated about45°, so that the splines of spider 48 are positioned to engage thehidden or dotted line portion of bore 46 as is shown in FIG. 7. Thecrane 7 now raises the lifting assembly 16 until the spider 48 abuts theupper surface of the stepped portion of bore 46 at which point it isengaged by and in the collar 44, as is shown in FIG. 8.

At this point in the procedure of connecting the lifting assembly 16 tothe inspection apparatus 14, the feet 60 of the ball and socketassemblies 50 are held about 3/16" above the leveling pads 52. Theleveling pads 52, as shown in FIG. 3, are connected to the upperportions of the support legs 20. A hydraulic cylinder 54 is nowactuated, causing its internal piston 56 to push against a fixed surface58 forcing the socket feet 60 into tight engagement with the levelingpads 52. Three non-adjustable base struts 65 are utilized to enhance thestructural rigidity of the lifting assembly 16 and are connected betweenthe three ball and socket assemblies 50, as is shown in FIG. 3. Asconnected, the base struts form a triangle, the center of which iscoincidental with the central axis of the lifting assembly 16 and themain column 24.

The inspection apparatus 14 is thereby fully secured to the liftingassembly 16 and is now suspended from the crane 7 for alignmentprocedures prior to being seated in the reactor vessel 10. Suchalignment procedures are necessary due to probable repositioning of themovable guide stud bushings 36 from site-to-site to accommodatediffering locations of the guide studs 32. In addition, the position andextension of manipulator arm 26 may be different from an inspectionstart at one site than at another. Further, the vessel locating key 62,shown in FIGS. 3 and 14, may or may not be in use. Consequently, the neteffect of these and other possible causes will be to present theinspection team with a different weight distribution at each inspectionsite, thereby necessitating the alignment procedure. Finally, even ifthe same weight distribution was expected, proper inspection techniquewould demand alignment verification.

The alignment procedure is carried out by turning one or more of theturnbuckle struts 64 which are rotatably adjustable and fixedlyconnected between the three ball and socket assemblies 50 and theslidable sleeve 66 of the hydraulic cylinder 54. Adjustment of theturnbuckle struts 64 has the effect of gimbaling the inspectionapparatus 14 about the center axis of the triangle formed by the basestruts 65 or the lower end of the lifting assembly 16. This enables theinspection team to plumb the main column 24 of the inspection apparatus14 and verify its vertical alignment. In addition, each of the threeball and socket assemblies 50 can be individually adjusted to shift theposition of the end of the turnbuckle strut 64 connected thereto toeffect adjustment of the inspection apparatus 14 with respect to boththe vertical and horizontal axes. Horizontal alignment is verified bychecking the level on any one of the three leveling pads 52.

The lifting assembly 16 is capable of being quickly disconnected byreversing the order specified above. First, the hydraulic cylinder 54 isdeactivated causing its outer sleeve 66 to move upwards lifting thesocket feet 60 from the leveling pads 52. The crane 7 now lowers thelifting assembly 16 by an amount sufficient to allow the spider 48 tofall out of engagement with the upper portion of the bore 46 of collar44. Spider 48 can now be rotated and withdrawn from collar 44. Afterthis is done, the entire lifting assembly can be removed by the crane 7,freeing it for other work, and leaving the inspection apparatus 14seated in the reactor vessel 10. Alternatively, the lifting assembly 16can be so disconnected after it has been used to remove the inspectionapparatus 14 from the reactor vessel 10, leaving the inspectionapparatus 14 on resting pads (not shown) or on the erection rig 5preparatory to shipment. By removing the lifting assembly 16 with theinspection apparatus 14 still seated in the reactor vessel 12, the workbridge 9 can be moved across the vessel pool 11 allowing for theperformance of other maintenance or inspection procedures or to assistin the vessel inspection itself.

Referring again to FIG. 3, there is shown three support legs 20A, 20Band 20C. Each of these is joined to the head support assembly 22 by aspacer 68 which is of a length appropriate to the diameter of the vesselto be inspected. It should be noted that for differing diameter reactorvessels, the spacers 68 and the support ring 18 are selected and sizedso that the guide stud bushings 36 extend radially to a point where theywill be aligned with and then engage the guide studs 32. Very smallvariations in radial dimensions are accommodated by loosening the guidestud bushing clamps 70 and inserting shims of an appropriate thicknesswhich would have the effect of moving the center of the guide studbushings 36 radially outward of support ring 18 as desired. It shouldalso be noted that the guide stud bushing clamps 70, when loosened,permit movement of the bushings 36 along the support ring 18 toaccommodate variations in the placement of the guide studs 32 in thevessel top flange 13 at different inspection sites.

As previously noted, the guide stud bushings 36 are movably connected tothe support ring 18 by the bushing clamps 70. As was also previouslynoted, the support ring 18 carries an annular key 19 about its outersurface. A keyway 71, see FIG. 4, cut in the surface of clamp 70, whichmates with support ring 18, accommodates key 19 and aligns the guidestud bushings 70 on support ring 18 with respect to the remainder of theinspection device 14. In addition, support legs 20A, 20B and 20C areconnected to support ring 18 respectively by a bracket 90, see FIG. 5,having a keyed hole 92 therethrough. Thus, the bracket 90 engages thekey 19 and positively locates and locks the support legs 20A, 20B and20C to support ring 18 which enhances the structural stability ofinspection apparatus 14. The leveling pads 52 are bolted or welded tothe upper segments of the support legs 20A, 20B and 20C in horizontalalignment and are utilized in the manner described above.

When seated within the reactor vessel 10, the three legs 20A, 20B and20C support the entire weight of the inspection apparatus 14. Stainlesssteel shoes 84 are bolted respectively to the bottom of support legs 20Band 20C. These shoes rest either on the circumferential vessel flange 15or on the core barrel flange (not shown), depending on whether the corebarrel has been removed. A special "A" shaped shoe 88 is bolted to theend of support leg 20A and is adapted to accurately position inspectionapparatus 14 as it is being seated within the reactor vessel 10. Withthe core barrel remaining in the vessel 12, a plate 94 having a keyway96 cut therein is bolted to shoe 88 as shown in FIGS. 12 and 13. As itis being seated, keyway 96 engages a head-to-vessel alignment pin, theposition of which is known, and positively locates the inspectionapparatus 14 within the vessel 10. As mentioned above, the clearancebetween the guide studs 32 and the guide stud bushings 36 is about 3/8"and their engagement yields a coarse circumferential alignment. Thesubsequent engagement by keyway 96 of the head-to-vessel alignment pinyields a fine circumferential alignment which provides for an absolutelycertain placement of the inspection apparatus 14 within vessel 10. Withthe core barrel removed for inspection, the plate 94 is removed fromshoe 88 and a vessel locating key 62, as shown in FIGS. 3 and 14, isbolted to shoe 88 in its place. The vessel locating key 62 fits into anotch 17 cut in the circumferential vessel flange 15, see FIG. 11, whichnotch is otherwise covered by the core barrel flange. This engagement ofnotch 17 by the vessel locating key 62 provides the same finecircumferential alignment means, with the core barrel removed, as wasyielded by the use of plate 94. It should be noted that plate 94 can bebuilt up with appropriately configured shims to accommodate thedifferent sized head-to-vessel alignment pins that may be encounteredfrom one vessel to another. Thus, by choice of the shoe 88configuration, in conjunction with the engagement of the guide studs 32by the guide stud bushings 36, the exact circumferential location ofsupport leg 20A, and derivatively that of manipulator arm 24, is knownand assured. In addition, this positive location or seating of theinspection apparatus is accomplished without touching or threatening thesealing surface of the vessel top flange 13.

Connected immediately below the head assembly 22, as shown in FIG. 3, isa gear box and motor assembly 72 which drives manipulator arm 26vertically along the main column 24 utilizing a pulley system 75. Themain column itself consists of several sections of flanged pipe boltedtogether. Sections may be readily removed or added to accommodate thedepth of reactor vessel inspection requirements. Each section isindividually encased so that water cannot enter therein. Between theflanges 85 thereof, the sections of main column 24 carry a track 78which is used, in conjunction with a sensor to be hereinafter described,to determine the extent of vertical travel or, alternatively stated, tofix the vertical position of manipulator arm 26. The main columnsections also include "U" shaped grooves 80 which accommodate bearingscarried by manipulator arm 26. The grooves 80 and flanges 85 combinefunctionally to restrain the manipulator arm 26 from making any unwantedor undesirable rotary movements about the main column 24 as it travelstherealong.

The manipulator arm 26, which is more clearly shown in FIG. 15, includesa carriage assembly 82 which rides on the main column 24 in the "U"shaped grooves 80. The carriage assembly 82 and the remainder ofmanipulator arm 26 would typically be fabricated from a low weightmaterial which can withstand the hostile operating environment. Thecarriage assembly 82 is fitted with internally mounted and sealed ballbearings which ride in and are engaged by the "U" grooves 80 andfacilitate vertical movements by manipulator arm 26 on the main column24. When the vertical drive motor (not shown) in the vertical motorassembly 72 is actuated, it rotates the drive pulleys 74 and 77 as isshown in FIG. 16. A pulley cable 79 is looped about the carriage idlerpulleys 76 and 81 and the head assembly idler pulleys 83 and 87. Whenthe vertical motor shaft 89 is rotated counterclockwise, the pulleycable 79 is released respectively by both drive pulleys 74 and 77 fromtheir take-up spools 91 and 93, lowering the manipulator arm 26 withequal force on both sides of the carriage assembly 82. This equalizationof the release force applied to both carriage idler pulleys 76 and 81insures that the carriage assembly will not be cocked and thereforehang-up or unduly wear its bearings at it travels down the main column24. Likewise, when the vertical motor drive shaft 89 is rotatedclockwise, the upward or lifting forces applied to the carriage idlerpulleys 76 and 81 is equalized and the carriage assembly 82, as well asthe remaining elements of manipulator arm 26, is lifted smoothly, at theproper attitude, up the main column 24. The head assembly idler pulleys83 and 87 serve to define the upper portion of the pulley cable loop.This upper portion of the cable loop is utilized to equalize any cableslippage or unbalance in the cable 79 which might otherwise unequallytend to pull up on or release idler pulleys 76 and 81. Thus, except forany movement to effect compensation due to an unbalance, the pulleycable 79 is in motion during vertial travel of the manipulator arm 26only between the drive pulleys 74 and 77 and the carriage idler pulleys76 and 81 respectively. An emergency cable clip 99 is secured to thecable 79 between the head assembly idler pulleys 83 and 87. If thepulley cable 79 should happen to snap, the clip 99 will become wedgedbetween one of the idler pulleys 83 or 87 and its respective supportbracket 95 or 97, thereby restraining further vertical movement ofmanipulator arm 26.

An emergency braking system 100 is shown in FIGS. 17, 18 and 19. Itserves to halt vertical movement of the manipulator arm 26 whenever itsvertical speed of travel exceeds a predetermined velocity, typically aspeed greater than five inches per second. A vertical velocity rateerror signal is developed utilizing a signal generated by the Z axisresolver 102 which engages the vertical track 78 and thereby follows andhelps to determine the vertical position and rate of change therein ofthe manipulator arm 26. When an overspeed condition is sensed by thecontrol system 30, an emergency brake signal is forwarded to threepneumatic cylinders 104 mounted beneath the carriage assembly 82. Thepneumatically operated piston 106 of each cylinder 104 is connected viaa header 108 to a brake shoe 110. The brake shoe 110 is fitted withspring loaded roller bearings 112 which ride in bearing slots 114 in thebrake show 110 and are normally urged against the "U" grooves 80 of themain column 24. In the rest position illustrated in FIG. 17, theemergency braking system 100 is disabled and the bearings 112 are springloaded against the " U" groove 80 holding the brake shoe 110 in its restposition and avoiding unnecessary wear. A cross-sectional view of thebrake shoe 100 and brake lining 116 is shown in FIG. 19.

When the emergency brake signal is received by the pneumatic cylinders104, the pistons 106 thereof are thrust upwardly at a speedsignificantly in excess of that exhibited by the manipulator arm 26,even in its overspeed condition. This rapid piston movement forces thewedge shaped brake shoe 110 upwardly into contact with the brake lining116 which is bolted to the bottom of the carriage assembly 82. As thebrake shoe 110 fully contacts the positionally fixed brake lining 116,as is shown in FIG. 18, the roller bearings 112 are forced inwardly inslots 1114 and the brake shoe 110 becomes jammed against the "U" groove80 halting further vertical movement of the manipulator arm 26. As notedabove, the speed of piston 106 is significantly greater than theoverspeed limit of the manipulator arm 26. It is therefore fast enough,when actuated, to overtake the manipulator arm 26 and cause brakingaction to occur even when the overspeed condition of manipulator arm 26results from upward movement thereof. Thus, the described emergencybraking system 100 functions to halt vertical movement of manipulatorarm 26 when an overspeed condition occurs regardless of the direction ofvertical or Z axis travel at that time. To insure absolute downwardrestraint of manipulator arm 26, an emergency stop plate 117, asdepicted in FIGS. 3 and 15, is bolted to the bottom section of maincolumn 24. Plate 117 serves to halt downward movement of manipulator arm26 should the emergency braking system 100 fail to function properly.The manipulator arm 26 is thereby prevented, by either the emergencybraking system 100 or the stop plate 117, from striking the bottom ofthe reactor vessel 10 or any portion thereof as it is vertically drivenin the vessel 10.

A axis motion or rotation of the manipulator arm 26 about the maincolumn 24 is shown in FIG. 15. As illustrated therein, actuation of theA axis motor 118 drives the carriage rotary gears 122 and 124 causingthe entire manipulator arm to swing about the main column 24. Theposition of manipulator arm 26 in the A axis is vertified by a signalwhich is generated by the rotary resolver 120. It should be noted withrespect to all of the drive motors described herein, whether shown ornot, that a resolver or position determining sensor is coupled theretoto provide a signal which is then employed to indicate the position ofmanipulator arm 26 or any portion thereof, in or about the particularaxis of movement associated with the motor being described.

Y axis movement, which is also indicated in FIG. 15, is achieved bydriving a set of telescoping arms 126 and 128, which are movable mountedwithin the carriage channels 130, toward and away from the carriageassembly 82. As is more clearly illustrated in the end view shown inFIG. 17, the Y axis motor 132 is coupled by its shaft 134 to a drivegear 136. When the Y axis motor 132 is actuated, it causes drive gear136 to be rotated, driving a rack 138 engaged thereby, which rack isbolted to the telescoping arm 126. This causes arm 126 to be driventowards or away from the carriage assembly 82, depending on thedirection of rotation of the Y axis motor 132. When the outertelescoping arm 126 is moved, it carries with it an idler gear 140 whichis meshingly engaged between rack 142, which is attached to the innertelescoping arm 128, and rack 144 which is coupled to the carriagechannel 130. For purposes of clarity, the illustration in FIG. 17depicts only one half of the telescoping arrangement of the Y axisdrive, but it will be understood that the Y axis motor 132 causes,through the action of another drive gear (not shown), both sets oftelescoping arms 126 and 128 to be driven in a desired direction alongthe Y axis.

Movement of the manipulator arm 26 along the Y axis is required, inparticular, to position the transducer array 28 within any one of thereactor vessel nozzles 38 for inspection thereof, as is shown in FIG. 9.In the event of total power failure or an inability to withdraw thetransducer array 28 from within a nozzle 38, an emergency retractionassembly 140 is provided. As is depicted in FIG. 21, the emergencyretraction assembly 140 includes a retraction cable 142 arranged withinthe carriage assembly 82 and extending therefrom to be looped about anidler pulley 144 which is rotatably mounted within and to thetelescoping arm 126. Cable 142 also is guided by the half-pulley 149.One end of the retraction cable 142 is fixedly secured to the carriageassembly 82 by a clamp 146. The other end of the retraction cable 142 isformed into a ring 150 which is detachably secured to the carriageassembly 82 at an initial position 152 by a removable clamp 148. Thering 150 is mounted so as to be accessible from above.

When an emergency retraction of the transducer array 28 becomesnecessary, a hook (not shown) is lowered into the reactor vessel 10 toengage the cable ring 150. Once engaged, the ring 150 is pulled up,which action frees the detechable clamp 148 from the carriage assembly82. Upward force is maintained, moving the cable ring 150 from itsinitial position 152 towards its final position 154. As the cable ring150 is pulled upwards toward its final position 154, the retractioncable 142 forces the pulley 144 from its initial position 156 to itsfinal position 158. Since the pulley 144 is secured to the outertelescoping arm 126, it forces it back into the carriage channel 130 asit moves towards its final position 158. Simultaneously, the outertelescoping arm 126 causes the inner telescoping arm 128 to be movedinwardly, through manual operation of the Y axis drive described above,thereby forcibly withdrawing the manipulator arm 26 and the transducerarray 28 from within a vessel nozzle 38.

B axis motion is obtained by actuating the B axis motor (not shown)which is mounted within the B axis drive housing 160 and connected tomounting bracket 178. As is more clearly illustrated in FIG. 22, the Baxis drive housing 160 is secured in the following manner. A mountingbracket 162 is bolted to each of the inner telescoping arms 128.Attached to the upper end portion of bracket 162 is an apertured dog ear164. Attached to the upper portion of the B axis drive housing 160 is amovable linkage assembly 166 which is actuated by a locked-over-centerlever 168. The linkage assembly 166 terminates in a dog 170 whichengages the aperture in dog ear 164 when lever 168 is moved to itslocked position 172 and holds the B axis drive housing in a normalposition with respect to the telescoping arm 128. The bottom portion ofthe B axis drive housing is movably secured by engagement with a hingepin 174.

As noted above, the transducer array 28 and manipulator arm 26 can bewithdrawn from a vessel nozzle 38 in an emergency situation. However, itmay not yet be safe to lift the inspection apparatus 14 from the vessel10 since the forward portion of the manipulator arm may strike thereactor vessel 10. Accordingly, after the manipulator arm 26 has beenmanually retracted, the hook is again lowered and engages the linkagelever 168. As the hook and lever 168 are pulled upwardly, the linkageassembly 166 extracts the dog 170 from engagement with the dog ear 164,allowing the B axis drive housing to rotate about hinge pin 174 as isshown in phantom in FIG. 22. With the B axis drive housing in its finalposition 176, the entire inspection apparatus 14 can be withdrawn fromthe vessel 10 without any fear of striking the vessel walls.

Further movement of the transducer array 28 is possible along or aboutfive additional axes of movement. In addition to movement of themanipulator arm 26, and derivatively movement of the transducer array28, along or about the A, B, Y and Z axis, movement can be effectedabout the C, D, E, F and G axes. The B axis motor shaft is connected toa mounting bracket 178 and, when driven, rotates bracket 178 and allelements connected forwardly thereof about the B axis. Two additionalmounting brackets 180 and 182 are secured to the B axis motor bracket178, as is shown in FIGS. 3 and 15. The C axis motor housing 184 iscoupled between and secured to the brackets 180 and 182 with the C axismotor shaft 186 extending through and being drivingly engaged by thebrackets 180 and 182. When actuated, the C axis motor drives its shaft186 and the brackets 180 and 182, as well as all of the manipulatorelements connected forwardly thereof, about the shaft 186. Motion in theD axis is achieved in a similar manner. The D axis motor housing 188 isalso coupled between and secured to the brackets 180 and 182 with the Daxis motor shaft 190 extending through and being drivingly engaged bythe brackets 180 and 182. When the D axis motor is actuated to drive itsshaft 190, motor shaft 190 and all of the manipulator arm elementsconnected forwardly thereof are rotated in the D axis. The E axis motorhousing 192 is connected to the C axis motor housing 188 with the E axismotor shaft (not shown) being connected to mounting bracket 194. Whenactuated, the E axis motor shaft drives bracket 194 about the E axis, aswell as all of the manipulator arm elements connected forwardly thereof.The F axis motor housing 196 is secured by mounting bracket 194 and bymounting brackets 198. The shaft 200 of the F axis motor (not shown)extends through and drivingly engages the mounting bracket 198, Whenactuated, the F axis motor drives its shaft 200 and the remainder of themanipulator arm elements connected forwardly thereof through F axismotion. The G axis motor housing 202 is secured to the end of mountingbracket 198. The G axis motor shaft 204 extends outwardly of housing 202and is clamped into the transducer plate collar 206 which, in turn, isclamped to the transducer array plate 40. When actuated, the G axismotor drives its shaft 204 and the transducer array plate about the Gaxis. Thus, the transducer array plate 40 and the transducer array 28mounted thereon, with reference to any point in the reactor vessel 10,can be driven in nine planes of movement or about nine axes of rotation.This highly mobile and segmented articulating drive train can beemployed to accurately position the transducer array 28 at any pointwithin the reactor vessel 10.

Ordinarily, electrical connection to and from the different motors,resolvers and the transducer array 28 would be accomplished by means ofcomponents particularly suited for use in an underwater operatingenvironment. To avoid the use of such special components, which are moreexpensive and require longer delivery times, it was decided topressurize the electrical cabling system allowing for the use ofordinary components. For example, the junction box 208, shown only inFIGS. 15 and 23 for purposes of clarity, can be pressurized to a degreewhich would prevent water seepage therein and thusly allow the use ofstandard electrical connectors. In order to conserve on cabling, the airsupply and electrical supply was combined in the cabling assembly 210,shown in FIG. 23. The illustration in FIG. 23 is merely representativeof the cabling assembly 210 and only one cable 212 and one dual cable214 has been shown, although more are used. The electrical cable 212carries a plurality of electrical conductors to and from the console 31which would typically include the control system 30. These conductorswould be utilized to energize the different motors and transducers andcarry signals which would report on transducer and resolver responses,among other things. The cable 212 is routed to the air supply junctionbox 216 which is sealed at its entry point therewith by a seal 218 toprevent air leakage from junction box 216. An air supply hose 220 isalso routed to the air supply junction box 216 and carries air at apressure significantly higher than atmospheric thereto. The air supplyhose 220 is sealingly connected by clamp 224 about an air receivingnozzle 222 extending from the junction box 216.

The cable 212 can either be through-routed through the junction box 216or terminated at a connector 225 provided for that purpose. In eitherevent, the cable 212 is routed from junction box 216 into the largercable or hose 214. Hose 214, with cable 212 disposed therein, includes agenerally annular space 215 along its length to carry the pressurizedair where needed. Cable 214 is clamped over nozzle 226 by clamp 228 toprovide an air-tight fit between the air supply junction box 216 and thedual hose 214. From junction box 216, the hose 214 is routed to theunderwater junction box 208. It is secured thereto by water-tight seals230 and 232 at the points where it enters junction box 208. From thejunction box 208, the hose 214 can be branched by internal connectors(not shown) to any one or more of the motors, resolvers, transducers,etc., used in the inspection apparatus 14. Further, since cable 214 candepart the junction box 208 carrying pressurized air, various motor andresolver housings can also be pressurized where desired.

As previously noted, the transducer array 28 is employed as theexamination means by which the integrity of the vessel welds 13 or anyappropriate portion of the vessel 10 can be inspected. A typical planview of the transducer array 28 disposed on the mounting plate 40 isshown in FIG. 24. It should be noted with respect to the individualtransducers themselves, that they are grouped or arrayed in a mannerwhich permits the manipulator arm 26 to optimally position the plate 40so that the greatest inspection flexibility results. For example, thethree transducers 240, 242, and 244 can be positioned, as illustrated inFIG. 25, to direct their ultrasonic beams to impinge at point 246 on thevessel 10. Transducer 242 can be oriented to impinge perpendicularly tothe vessel wall at point 246 to verify the water path distance or tocheck for vessel flaws. Transducers 240 and 244 can be used to directangled beams at point 246 which may be a weld point or material adjacentthereto. Further, transducers 240 and 244 may be coupled to pitch-catchor merely echo their respective beams.

The individual transducers are secured to plate 40 by a transducermounting assembly, generally designated 250, shown in FIGS. 26 and 27 inits normal orientation. The transducer mounting assembly includes ahollow, generally rectangularly shaped bar 252 having a slot 254 cutlongitudinally therein. The bar 252 is bolted to the transducer plate 40by bolts 256 one of which is shown in FIG. 27. A circular bar 258 iscaptured at either end thereof by holders 260 and fastened securelytherein by set screws 262. The holders 260 are secured to the transducerplate 40 by bolts 264, also shown in FIG. 27, parallel to and spacedapart from bar 252.

A transducer 244 is held in a retaining block 266 having a circular bore268 therein sized to accommodate the transducer 244. The top portion ofbore 268 is countersunk or cut away to accept and support the flange 245of transducer 244 in the circular shelf 270. Plates 272, which arefitted over and about the transducer flange 245 and secured to the topof retaining block 266 by bolts 274, tightly capture and retain thetransducer 244 in the block 266. If necessary, the transducer 244 can berotated in the retaining block by loosening the bolts 274. The retainingblock 266 includes upstanding flanges 276 and 278 having circular bores280 and 282 cut therethrough for respectively accepting a hinge pin 284therein.

The retaining block 266 is, in turn, secured to a yoke 286 which alsoincludes two upstanding flanges 288 and 290, each having a circular bore292 and 294 cut respectively therein. The hinge pin 284 extends throughthe bores 280 and 292 to pivotally fasten one side each of the block 266and the yoke 286 to each other. A set screw 296, extending from the topof flange 276 through a bore 298 therein is used to clamp the hinge pin284 to the retaining block 266. The other end of hinge pin 284 remainsfree to rotate in bore 292 of flange 288. The other side of retainingblock 266 is also pivotally secured to the yoke 286 by a hinge pin 300,which is "T" shaped in cross-section. The leg of hinge pin 300 extendsthrough the bores 282 and 294 of flanges 278 and 290. It is securedwithin bore 282 and clamped to flange 278 by a set screw 302. The headportion of hinge pin 300 abuts the flange 290 and is captured by a "U"shaped clamp 304 which is bolted to flange 290. The leg portions 306 and308 of clamp 304 are held together by a bolt 310 which is threadedthrough bores 312 and 314 cut respectively in leg portions 306 and 308.When the bolt 310 is tightened down, leg portions 306 and 308 are drawntightly together about the head portion of hinge pin 300 preventing itfrom turning in clamp 304. When bolt 310 is loosened, however, thetransducer 244 and the retaining block 266 can be pivoted about thehinge pins 284 and 300. A side view of a pivoted restraining block 266,with transducer 244 having been tilted forwardly, is shown in FIG. 31.An exploded isometric view of the transducer 244, restraining block 266and yoke 286 coupling is illustrated in FIG. 33.

As shown in FIGS. 26 and 31, two circular sleeves 320 and 322 are fitover and slid along the circular bar 258 prior to its being clamped intothe holders 260. The sleeves 320 and 322 are bolted to one side of theyoke 286 by bolts 321. An angle bracket 324 is secured to the other sideof yoke 286 by bolts 326. The perpendicular portion of bracket 324 isbolted to the rectangular bar 252 by the end bolts 328. If bolts 328 areloosened, the yoke 286 and therefore the transducer 244 held therein canbe moved transversely along the bars 252 and 258.

The bolts 328 pass through a bore 325 in the perpendicular portion ofbracket 324 as illustrated in FIGS. 27, 30 and, most clearly, 32. Afterpassing through the bore 325, the bolts extend through plate 340 and theslot 254 into the bar 252. The legs 330 of bolts 328 are threadedthrough the barrel nuts or pivots 342 and are pierced by cotter pins 344at their terminal point to prevent their being worked out of the barrelnuts 342. A centered bolt 346 is threaded through the perpendicularportion of bracket 324 and abuts the plate 340 which acts as a stoptherefor. When a locknut 348 is loosened, the bolt 346 can be tighteneddown, increasing the distance between plate 340 and the bracket 324,thereby pivoting the yoke 286 about the circular bar 258. An example ofa pivoted yoke 286 is shown in FIG. 30. When the bolt 346 is tightened,the barrel nuts 342 pivot in the slot 254 permitting the yoke 286 tomove to its canted position. It should be noted that the end bolts 328are not loosened to effect or aid in this pivoting motion of the yoke286. A number of bolt head flanges 350 are used to cover and retainvarious bolts should they loosen and work out of engagement.

As the transducer array 28 is disposed about the vessel 10, particularlyin or near one of the nozzles 38, it becomes difficult because of thecurved vessel surfaces, to maintain one of the transducers perpendicularto the vessel wall and simultaneously insure proper clearances. For thatreason, at least two transducers 370 and 372 are mounted on upstandingbrackets 374 and 376 rather than on the bars 252 and 258. An example ofthis mounting arrangement is depicted in FIGS. 28 and 29. Therestraining block 266 is removed from the yoke 286 and is bolted to thebrackets 374 and 376. It is then pivoted at an appropriate angle byloosening bolt 310 of the "U" clamp 304 as previously described. In thiscase, however, clamp 304 is bolted to the block 266 rather than the yoke286.

As shown in FIG. 29, the transducer beam 380 can be directed against thecurved vessel wall 382, generally normal thereto, and the sametransducer can be employed to receive the echo. Thus, the perpendiculardistance between the transducer plate 40 and the vessel wall 382 can becontinuously monitored. Utilizing such information, the manipulator arm26 can be moved accordingly to prevent collisions. Thus, there has beendescribed a versatile transducer mounting assembly which tightly retainsa transducer therein, but which can be adjusted to permit translational,pivotal and rotary motion of the transducer relative to the mountingplate.

While the invention has been shown and described herein in considerabledetail, such disclosure is to be considered as only illustrative orexemplary in character and not restrictive, as within the broad scope ofthe invention, modifications of or alternatives thereto may readilysuggest themselves to persons skilled in this art.

I claim:
 1. In a device for inspecting a nuclear reactor vessel whileseated therein, the device having a central column, a manipulator armand drive means for extending and retracting the arm, apparatus formanually retracting the arm from an extended position thereof in theevent of power failure, when the arm is under water said apparatuscomprising:a. a member adapted for engagement by a cable connected tothe manipulator arm frame at a point remote from the central column andcooperably coupled to the drive means for extending and retracting thearm; b. A cable clamped fixedly at one end thereof to the manipulatorarm frame at a point near the central column and routed to engage saidmember; and c. clamping means for detachably securing said cable at itsother end to the manipulator arm frame at a point near the centralcolumn which is accessible from above the vessel.
 2. The apparatusaccording to claim 1 wherein said member comprises an idler pulley aboutwhich said cable is looped and a bracket for securing said idler pulleytherein.
 3. The apparatus according to claim 2 wherein the end of saiddetachably clamped cable is formed into a ring.
 4. The apparatusaccording to claim 3 which additionally comprises bearing guide meanspositioned within the manipulator arm between the locations at which theends of said cable are clamped and said member is connected for guidingsaid cable, as it is pulled, to exert maximum retration force on saidmember.